Whether threatens the Earth mass extinction of species

. The rate of extinction of species of plants and animals in our time is quite high. It is noted by many scholars. In some regions of the Earth is greatly reduced biodiversity, reduced the number of large animals. Biologists started talking about the sixth global extinction occurred, incidentally, is not without human intervention. Opponents of such alarmism insist that to speak of the catastrophe definitely will be in a century or more.

«What on the planet now, there is a high rate of extinction of species is an indisputable fact. Another thing accurate assessment of the rate and its comparison with mass extinctions of past ages» — told RIA Novosti, Alexander Markov, head of the Department of biological evolution, biological faculty of MSU named after M. V. Lomonosov.

Paleontologists claim that some of the background species extinction, and the emergence of new, happens on the planet constantly. But now, species are disappearing a thousand times faster than in a peaceful prehistory. This is the conclusion reached by the authors of the international research project «Millennium Ecosystem Assessment» published in 2005. According to scientists, the disappearance threatens 10-30% of the species.

In 2009, the Australian biologist, Nigel stork (Nigel E. Stork) analyzed the extinction rates predicted by various researchers. The spread turned out, at first glance, is impressive: every ten years the planet loses a tenth of a percent, for example among the insects, up to tens of percent of the total number of species.

«Even 1-2% is very much. It means losing every hundredth appearance in ten years on the planet. And if 20-30%? Yes, very similar to a major mass extinction,» — says Markov’s work well, kids.

More likely to disappear have large animals, says Leonard Polishchuk, leading researcher of the Department of General ecology Biological faculty Moscow state University. That is the conclusion he came studying the extinction of the mammoth fauna in the Pleistocene. The fact that the large animals form a numerous population, in other words, elephants smaller than mice. If the population of large animals is reduced under the influence of some factors, the reduced genetic diversity of the species accumulate harmful mutations that are pushing animals to extinction. Build positive feedback when some factors reinforces the other, and as a result, the form disappears.

«There are cases when species have recovered after the sharp decline in numbers. The most famous example is the cheetahs. Judging by their genes, five or ten thousand years ago, they were, figuratively speaking, through a very narrow bottleneck. There were only a few dozen individuals. But the sight had miraculously survived. All modern cheetahs are descendants of those individual animals» — gives an example of Markov.

CC BY 2.0 / James Temple / CheetahВсе modern cheetahs are close relativesCC BY 2.0 / James Temple / CheetahВсе modern cheetahs are close relatives

American botanist Peter Raven (Peter Raven) in a recent article «The Fate of the World’s Plants» (the Fate of the plant world) admits that half of species threatened with extinction before the end of the century. Moreover, most of them remain unknown to us.

But mentioned the stork in 2013, claimed the opposite in a witty work entitled «will we be Able to count all the species before they die out?» Not sharing hypotheses about the sixth mass extinction, a scientist and his co-authors have listed factors that hinder us to accurately assess the rate of loss of biodiversity: the conservation of the species, man-made landscapes, inhabited by many species, delayed extinction (extinction debt), which lags behind in time from their causes, as well as the notorious human factor. After all, to the disappearance of 90% of the known species of birds and mammals over the last hundred years, people somehow had a hand.

Super-efficient megahit

«About 40 thousand years ago, when people come to Australia, they began to die EN masse in large animals. Most likely, this is directly related to the person. The Australian megafauna were not adapted to a coexistence with this super-efficient a predator as the person», — says Alexander Markov.

Around the same time considerably thinned megafauna in the tundra found in Eurasia. Extinct mammoths, cave lions and bears, woolly rhinos and ancient horses. Scientists believe that the disappearance is due to several reasons, including the onset of the interglacial. And besides, at this time released from the glacier site, dwelt in a well-organized ancient hunters with bows and spears. According to Markov, the human role in the extinction of large animals in the late Paleolithic, it is possible to tell, proved.

Climate and life

Climate change (regardless of underlying causes) is considered as one of the main factors of contemporary extinctions. This relationship was examined by scientists from Russia and the United States, based on the mathematical model of the emergence of chaos in a population of organisms. They added in the model is positive feedback when the climate affect the ecosystem and Vice versa. «There are enough resources and a good climate, and species are dying EN masse. It would seem that there is no logic there. But it turns out that works a positive feedback,» says co-author Ivan Sudakov, the employee of physical faculty of the University of Dayton in the United States.

In another article, published while in Arxiv.org the same authors showed that a population of organisms, reaching a maximum diversity, having a lot of resources that can become extinct from small fluctuations in climate.

Could we apply such models to our time? This opportunity allows Daniel Rothman (Daniel H. Rothman) of MIT in a recent article «Thresholds of catastrophe in the Earth system» (the Beginning of the disasters in the system Earth). It analyzes the saturation of the Earth’s atmosphere with carbon dioxide over the past 540 million years, trying to understand when and under what conditions the trouble starts key systems of the planet, leading to the extinction of species.

Earth has experienced five disasters, losing a large part of the inhabitants as a result of restructuring of the atmosphere, volcanic activity, asteroid attack, and a combination of a variety of circumstances. After each episode of the living world was restored millions of years. If he can handle six?